Microsoft has set a kill-by date for a mobile email app that enterprises have long relied on, telling customers they must switch to another company app in two months.

The Outlook Web App (OWA) for iOS and Android will stop working May 15, Microsoft announced last week. “On May 15, 2018, the OWA mobile apps will stop working,” Eugenie Burrage, of the firm’s product marketing team, wrote in a March 6 post to a company blog. “Office 365 users who attempt to open them will be greeted with a message directing them to download Outlook for iOS or Android.”